1. Field of the Invention
The present invention relates to a multi-functional electronic desk calculator having various functions as well as ordinary arithmetic four-rules calculation.
2. Description of the Related Art
In a multi-functional electronic desk calculator having various functions, such as a functional calculation, a complex number calculation, a numerical-value integral calculation, statistical calculation, a time calculation and/or a unit conversion as well as four-rules calculation, it is required to reduce the number of keys at a key input portion thereof.
In an electronic desk calculator known by the inventors of the present application, which can perform a time calculation or an angle calculation by inputting a hexagesimal numerical value, a hexagesimal input key and a hexagesimal conversion key are discretely provided in the key input portion together with ten keys, four-rules keys, a decimal-point key and an equal key.
The hexagesimal input key is used for recognizing a hexagesimal number in case that a numerical value inputted through the ten keys is hexagesimal number. For example, when a numerical value of angle is inputted as a hexagesimal number, a numerical value corresponding to the degree portion of the angle is inputted by means of the ten keys, and the input of the degree portion is recognized by depressing the hexagesimal input key. Then, a numerical value corresponding to the minute portion is inputted and the hexagesimal input key is pressed to recognize as the minute portion. Thereafter a numerical value corresponding to the second portion is inputted and the hexagesimal key is depressed.
The hexagesimal conversion key is used in case that a decimal numerical value which was inputted through the ten keys is to be converted into a hexagesimal numerical value.
As mentioned above, in the electronic desk calculator, since the two keys are discretely provided to convert a numerical value into a hexagesimal number, the number of keys increases and operations of the keys become complex causing misoperations.
In an electronic desk calculator having mutual conversion functions for a plurality of units, which is known by the inventors of the present application, two unit-conversion direction selecting keys and a numeral-value erasing key are discretely provided in an input portion thereof in addition to ten keys, four-rules keys, functional keys, a decimal point key, memory statistic keys, a percent key and an equal key.
The ten keys, the four-rules keys, the functional keys, the decimal point key, the memory statistic key, the percent key and the equal key also serve as unit-conversion executing keys respectively. These keys are assigned for units to be converted respectively, and symbols of the assigned units are displayed over, below or on the right sides of the respective keys. For example, for a key of "8", which is one of the ten keys, a symbol of unit conversion such as "in.revreaction.cm" is displayed as well as the numeral value of "8".
One of the two unit-conversion direction selecting keys are depressed when unit conversion of an numeral value inputted through the ten keys is carried out. Either of these keys is selectively depressed in accordance with the direction of the unit conversion. For example, in case that "100" inches is to be converted into a numeral value of centimeter, the numeral value of "100" is inputted through the ten keys at first. Then one of the two unit-conversion direction selecting keys, which indicates the conversion from the left side unit to the right side unit is depressed. Thereafter, the key of "8" among the ten keys, which is also used as a unit-conversion executing key for "in.revreaction.cm", is depressed, thereby obtaining a display of "254" designating the corresponding numeral value of the centimeter unit at a display portion.
While, the numeral-value erasing key is operated when a wrong numeral value is inputted through the ten keys so as to successively erase the lowest digit by shifting the displayed numeral value in the right direction.
In the aforementioned desk calculator, since the two unit-conversion direction selecting keys and the numeral-value erasing key each having a sole function are discretely provided, the number of the keys is increased.
According to the such desk calculator, furthermore, it is necessary that an operator reads symbols displayed above, below or on the right sides of the respective keys used for the unit conversion execution, and the operator must selectively press one of the unit-conversion-direction selecting keys first, then depress the desired unit-conversion executing key. Therefore, operations become complex causing misoperation. Additionally, since information concerning the conversion unit is not displayed at the display portion, the operator does not occasionally notice when misoperations occur.